Flat fluorescent letter display tubes

Claim 1

In a flat fluorescent letter display tube of the type wherein a plurality of letter display units are arranged on a straight line on an insulative substrate, each of said letter display units having a plurality of segment electrodes arranged in a predetermined configuration, an electrode provided with perforations adapted to contain said segment electrodes and a control grid mounted on said perforated electrode to cover sAid perforations and said segment electrodes and disposed in a sealed envelope including a transparent upper half and a lower half which are joined together in an air tight fashion, said display tube further comprises a plurality of filament supports mounted on said substrate on both sides of the array of said letter display units, a plurality of filaments mounted on the opposing filament supports, such that at least one filament extends above each letter display unit, the improvement in which said plurality of segment electrodes, terminals for said electrodes with perforations, terminals for said filaments and a metal film are printed on said substrate; and means for heating said metal film and air tightly joining said upper half to said substrate thereby completing said sealed envelope.